1. The ordinal number matching the number six in a series.
2. One of six equal parts.
a. An interval of six degrees in a diatonic scale.
b. A tone separated by this interval from a given tone.
c. The harmonic combination of two tones separated by this interval.
d. The sixth tone of a scale; the submediant.
sixth adv. & adj.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.